diff --git a/apps/arstack_studio/qml/SignalMatrix.qml b/apps/arstack_studio/qml/SignalMatrix.qml
index 2e6d9d242..1c84e2b43 100644
--- a/apps/arstack_studio/qml/SignalMatrix.qml
+++ b/apps/arstack_studio/qml/SignalMatrix.qml
@@ -124,12 +124,14 @@ Rectangle {
                 property real pendingMagnitude: mag
                 property real pendingPhase: angle
 
-                // The same placement/visibility semantics for mouse and keyboard.
-                // Clamp horizontally to the row rather than allowing a 250px
-                // popup to extend underneath the adjacent matrix.
+                // Align with the field edge, not the left side of the table.
+                // Clamp inside the owning matrix and open below the editor;
+                // keyboard Menu/Shift+F10 uses exactly the same placement.
                 function openFieldMenu(field, actionMenu) {
-                    const at = signalRow.mapFromItem(field, 0, field.height)
-                    actionMenu.popup(Math.max(6, Math.min(at.x, signalRow.width - actionMenu.width)), at.y)
+                    const edge = signalRow.mapFromItem(field, field.width, field.height)
+                    const x = Math.max(6, Math.min(edge.x - actionMenu.width,
+                                                   signalRow.width - actionMenu.width - 6))
+                    actionMenu.popup(x, edge.y + 3)
                 }
 
                 // Action-backed menu uses a single globally styled delegate.
@@ -139,7 +141,7 @@ Rectangle {
                     id: magnitudeMenu
                     theme: matrix.theme
                     uiFont: matrix.uiFont
-                    title: "Magnitude · " + signalRow.sid
+                    contextLabel: "Magnitude · " + signalRow.sid
                     commandRows: 4
                     Action {
                         text: "Zero · 0"
@@ -170,7 +172,7 @@ Rectangle {
                     id: phaseMenu
                     theme: matrix.theme
                     uiFont: matrix.uiFont
-                    title: "Angle · " + signalRow.sid
+                    contextLabel: "Angle · " + signalRow.sid
                     commandRows: 3
                     Action {
                         text: "Zero angle · 0°"
diff --git a/apps/arstack_studio/qml/StudioActionMenu.qml b/apps/arstack_studio/qml/StudioActionMenu.qml
index a026db163..6395c42a1 100644
--- a/apps/arstack_studio/qml/StudioActionMenu.qml
+++ b/apps/arstack_studio/qml/StudioActionMenu.qml
@@ -7,11 +7,17 @@ Menu {
     id: actionMenu
     property var theme
     property string uiFont: "Inter"
+    // The native Menu.title reserves a heading area even when a dark
+    // custom menu delegate does not paint it. That produces the oversized
+    // blank top area visible in the previous Windows context popup.
+    // Keep context for accessibility/diagnostics without a title header.
+    property string contextLabel: ""
+    title: ""
     property int commandRows: 4
     property int dividerRows: 1
     popupType: Popup.Item
-    width: 212
-    height: commandRows * 29 + dividerRows * 7 + 8
+    width: 204
+    height: commandRows * 30 + dividerRows * 7 + 8
     topPadding: 4
     bottomPadding: 4
     leftPadding: 4
@@ -22,20 +28,21 @@ Menu {
     delegate: MenuItem {
         id: actionItem
         width: actionMenu.width - actionMenu.leftPadding - actionMenu.rightPadding
-        implicitHeight: 29
+        implicitHeight: 30
         leftPadding: 8
         rightPadding: 8
         font.family: actionMenu.uiFont
         font.pixelSize: 11
         contentItem: RowLayout {
-            spacing: 7
+            spacing: 9
             Image {
                 visible: actionItem.icon.source.toString().length > 0
                 source: actionItem.icon.source
-                sourceSize.width: 24
-                sourceSize.height: 24
-                Layout.preferredWidth: visible ? 15 : 0
-                Layout.preferredHeight: 15
+                sourceSize.width: 18
+                sourceSize.height: 18
+                Layout.preferredWidth: visible ? 16 : 0
+                Layout.preferredHeight: 16
+                fillMode: Image.PreserveAspectFit
                 opacity: actionItem.enabled ? 0.95 : 0.33
             }
             Text {
@@ -48,7 +55,7 @@ Menu {
             }
         }
         background: Rectangle {
-            radius: 4
+            radius: 5
             color: actionItem.highlighted ? actionMenu.theme.menuHover : "transparent"
             border.width: actionItem.activeFocus ? 1 : 0
             border.color: actionMenu.theme.accent
diff --git a/apps/arstack_studio/tests/check_operator_workspace.py b/apps/arstack_studio/tests/check_operator_workspace.py
index c9fa6afd1..af471e7e1 100644
--- a/apps/arstack_studio/tests/check_operator_workspace.py
+++ b/apps/arstack_studio/tests/check_operator_workspace.py
@@ -127,7 +127,15 @@ def main() -> None:
             "context actions must stay compact, descriptive and grouped")
     assert "implicitHeight: 65" in source("RibbonAction.qml")
     assert 'hovered ? "#142334"' in source("RibbonAction.qml")
-    assert "width: 212" in menu and "commandRows * 29" in menu
+    require('title: ""' in menu and 'property string contextLabel: ""' in menu
+            and 'contextLabel: "Magnitude · "' in matrix
+            and 'contextLabel: "Angle · "' in matrix
+            and 'title: "Magnitude · "' not in matrix and 'title: "Angle · "' not in matrix,
+            "context menu must have no phantom native title/header blank space")
+    require("width: 204" in menu and "commandRows * 30" in menu
+            and "actionMenu.popup(x, edge.y + 3)" in matrix
+            and "signalRow.mapFromItem(field, field.width, field.height)" in matrix,
+            "context menu must align to the editor with compact deterministic geometry")
     assert "text: \"Generated setpoint · not independent on-wire proof\"" not in preview
     assert "No ESP32 board detected · Preview mode only" in main_qml
     require("Layout.preferredHeight: 57" in main_qml